3-Hydroxy-4-methoxyphenyl aryl carbonates

ABSTRACT

Novel 3-hydroxy-4-alkyloxyphenyl aryl carbonates particularly well suited as sweeteners in foodstuff, said carbonates having the following basic structure: ##STR1## .

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a novel group of compounds and more particular to a novel group of compounds particularly well suited as sweeteners in edible foodstuff.

2. Description of the Prior Art

Sweetness is one of the primary taste cravings of both animals and humans. Thus, the utilization of sweetening agents in foods in order to satisfy this sensory desire is well established.

Naturally occuring carbohydrate sweeteners such as sucrose, are still the most widely used sweetening agents. While these naturally occurring carbohydrates, i.e., sugars, generally fulfill the requirements of sweet taste, the abundant usage thereof does not occur without deleterious consequence, e.g., high caloric intake and nutritional imbalance. In fact, oftentimes the level of these sweeteners required in foodstuffs is far greater than the level of the sweetener that is desired for economic, dietic or other functional consideration.

In an attempt to eliminate the disadvantages concomitant with natural sweeteners, considerable reasearch and expense have been devoted to the production of artificial sweeteners, such as for example, saccharin, cyclamate, dihydrochalacone, aspartame, etc. While some of these artificial sweeteners satisfy the requirements of sweet taste without caloric input, and have met with considerable commerical success, they are not, however, without their own inherit disadvantages. For example, many of these artificial sweeteners have the disadvantages of high cost, as well as delay in the perception of the sweet taste, persistent lingering of the sweet taste, and a very objectionable bitter, metallic aftertaste when used in food products.

Since it is believed that many disadvantages of artificial sweeteners, particularly aftertaste, is a function of the concentration of the sweetener, it has been previously suggested that these effects could be reduced or eliminated by combining artificial sweeteners such as saccharin, with other ingredients or natural sugars, such as sorbitol, dextrose, maltose etc. These combined products, however, have not been entirely satisfactory either, Some U.S. Patents which disclose sweetener mixtures include for example, U.S. Pat. No. 4,228,198; U.S. Pat. No. 4,158,068; U.S. Pat. No. 4,154,862; U.S. Pat. No. 3,717,477.

Also much work has continued in an attempt to develop and identify compounds that have a sweet taste. For example, in Yamato, et al., Chemical Structure and Sweet Taste Of Isocoumarin and Related Compounds, Chemical Phmaraceutical Bulletin, Vol. 23, p. 3101-3105 (1975) and in Yamato et al. Chemical Structure and Sweet Taste Of Isocoumarins and Related Compound, Chemical Senses And Flavor, Vol. 4 No. 1, p. 35-47(1979) a variety of sweet structures are described. For example, 3-Hydroxy-4-methoxybenzyl phenyl ether is described as having a faint sweet taste.

Despite the past efforts in this area, resarch continues. Accordingly, it is desired to find a compound that provides a sweet taste when added to foodstuff or one which can reduce the level of sweetener normally employed and thus eliminate or greatly diminish a number of disadvantages associated with prior art sweeteners.

SUMMARY OF THE INVENTION

This invention pertains to a compound of the formula: ##STR2## wherein: R is methyl;

R₁ is ##STR3## each R₂ is selected from the group consisting of H, OH, CH₃, CH₂,CH₃, OCH₃, CH₂ OH, CH₂ CH₂ CH₃, CH(OH)CH₃, CH(CH₃)₂, OCH₂ CH₃, CH₂ OCH₃, CH₂ CH₂ OH, COCH₃, COCH₂ CH₃, CH₂ COCH₃, COOH and COOCH₃ ; and

each R₃ is selected from the group consisting of H, CH₃, CH₂ CH₃ and OCH₃ ;

with the proviso that R₁ contain no more than 12 carbon atoms; and salts thereof.

It is found that these compounds have a sweet taste and function as a low calorie sweetening agent when employed with a foodstuff.

DESCRIPTION OF THE PREFERED EMBODIMENTS

In accordance with the present invention, the preferred novel compounds are of the formula: ##STR4## wherein: R is methyl;

R₁ is ##STR5## each R₂ is selected from the group consisting of H, OH, CH₃, CH₂ CH₃, OCH₃, CH₂ OH CH₂ CH₂ CH₃, CH(OH)CH₃, CH(CH₃)2, OCH₂ CH₃, CH₂ OCH₃, CH₂ CH₂ OH, COCH₃, COCH₂ CH₃, CH₂ COCH₃, COOH and COOCH₃ ; and

each R₃ is selected from the group consisting of H, CH₃, CH₂ CH₃ and OCH₃ ;

with the proviso that R₁ contain no more than 12 carbon atoms; and salts thereof.

Preferably R₁ will contain no more than 10 carbon atoms and more preferably will contain no more than 8 carbon atoms.

Illustrative compounds within the above formula include:

3-hydroxy-4-methoxyphenyl phenyl carbonate

3-hydroxy-4-methoxyphenyl 2-hydroxyphenyl carbonate

3-hydroxy-4-methoxyphenyl 2-methylphenyl carbonate

3-hydroxy-4-methoxyphenyl 3-methylphenyl carbonate

3-hydroxy-4-methoxyphenyl 2-acetylphenyl carbonate

3-hydroxy-4-methoxyphenyl 2,6-dihydroxyphenyl carbonate

3-hydroxy-4-methoxyphenyl 2-methoxyphenyl carbonate

3-hydroxy-4-methoxyphenyl 3-methoxyphenyl carbonate

3-hydroxy-4-methoxyphenyl 2,6-dimethoxyphenyl carbonate

3-hydroxy-4-methoxyphenyl 2,5-dimethylphenyl carbonate

3-hydroxy-4-methoxyphenyl 2,5-dimethoxyphenyl carbonate

3-hydroxy-4-methoxyphenyl 2,6-dimethylphenyl carbonate

3-hydroxy-4-methoxyphenyl 3,5-dimethylphenyl carbonate

3-hydroxy-4-methoxyphenyl 3,5-dimethoxyphenyl carbonate

3-hydroxy-4-methoxyphenyl 2-propylphenyl carbonate

3-hydroxy-4-methoxyphenyl 2-isopropylphenyl carbonate

3-hydroxy-4-methoxyphenyl 2-ethoxyphenyl carbonate

3-hydroxy-4-methoxyphenyl 2-(hydroxymethyl)phenyl carbonate

3-hydroxy-4-methoxyphenyl 2-(hydroxyethyl)phenyl carbonate

3-hydroxy-4-methoxyphenyl 2-(methoxymethyl)phenyl carbonate

3-hydroxy-4-methoxyphenyl 2-methyl-6-methoxyphenyl carbonate

3-hydroxy-4-methoxyphenyl 2-methyl-6-ethylphenyl carbonate

3-hydroxy-4-methoxyphenyl 2,5,6-trimethylphenyl carbonate

3-hydroxy-4-methoxyphenyl 2-methyl-6-hydroxyphenyl carbonate

These novel compounds are effective sweetness agents when used alone or in combination with other sweeteners in foodstuffs. For example, other natural and/or artificial sweeteners which may be used with the novel compounds of the present invention include sucrose, fructose, corn syrup solids, dextrose, xylitol, sorbitol, mannitol, acetosulfam, thaumatin, invert sugar, saccharin, cyclamate, dihydrochalcone, hydrogenated glucose syrups, aspartame (L-aspartyl-L-phenylalanine methyl ester) and other dipeptides, glycyrrhizin and stevioside and the like.

Typical foodstuffs, including pharmaceutical preparations, in which the sweetness agents of the present invention may be used are, for example, beverages including soft drinks, carbonated beverages, ready to mix beverages and the like, infused foods (e.g. vegetables or fruits), sauces, condiments, salad dressings, juices, syrups, desserts, including puddings, gelatin and frozen desserts, like ice creams, sherbets and icings, confections, toothpaste, mouthwash, chewing gum, cereals, baked goods, intermediate moisture foods (e.g. dog food) and the like.

In order to achieve the effects of the present invention, the compounds described herein are generally added to the food product at a level which is effective to perceive sweetness in the food stuff and suitably is in an amount in the range of from about 0.0005 to 2% by weight based on the consumed product. Greater amounts are operable but not practical. Preferred amounts are in the range of from about 0.001 to about 1% of the foodstuff. Generally, the sweetening effect provided by the present compound is experienced over a wide pH range, e.g. 2 to 10 preferably 3 to 7 and in buffered and unbuffered formulations.

It is preferred that when the compounds are used in the foodstuff that the compounds have a sucrose equivalency of at least 1 percent by weight, more preferrably that they have a sucrose equivalency of at least 5 percent by weight and most preferrably they have a sucrose equivalency of at least 7 percent by weight.

A taste procedure for determination of sweetness merely involves the determination of sucrose equivalency. Sucrose equivalence for sweeteners are readily determined. For example, the amount of a sweetener that is equivalent to 10 weight percent aqueous sucrose can be determined by having a panel of tasters taste the solution of a sweetener and match its sweetness to the standard solution of sucrose. Obviously, sucrose equivalents for other than 10 weight percent are determined by matching the appropriate sucrose solutions.

It is desired that when the sweetener agent of this invention is employed in combination with another sweetener the sweetness equivalent of the other sweetener is equal to or above about 1 percent sucrose equivalent. Preferably the combination of sweeteners provides a sucrose equivalent in the range of from about 3 weight percent to about 40 weight percent and most perferably 4 weight percent to about 15 weight percent.

In order to prepare the compounds of the present invention an esterification reaction is employed. A 3-benzyloxy-4-R-oxyphenol is esterified with a chloroformate of the R₁ moiety (e.g., R₁ OCOCl). This provides a 3-benzyloxy-4-R-oxyphenyl R₁ carbonate. This is subsequently converted to the desired 3-hydroxy-4-R-oxyphenyl R₁ carbonate.

To obtain 3-benzyloxy-4-methoxyphenol, isovanillin which is also known 3-hydroxy-4-methoxybenzaldehyde is used as a starting material. Isovanillin is a commercially available material. Isovanillin is converted to 3-benzyloxy-4-methoxybenzaldehyde which is then converted to 3-benzyloxy-4-methoxyphenyl formate by the following reactions.

Performic acid is prepared by first heating a mixture of 30% by weight hydrogen peroxide and 97% by weight formic acid in a weight ratio of 1:5 to 60° C. and then cooling the mixture in an ice bath. The mixture is then added dropwise over a three hour period to an ice-cold 1M solution of 3-benzyloxy-4-methoxybenzaldehyde in methylene chloride. After the addition is completed a saturated solution of sodium bisulfite is added dropwise until the mixture exhibits a negative starch-iodide test for peroxides. The reaction mixture is poured into an equal volume of water. The phases separate and the aqueous phase is extracted with two parts of methylene chloride per part of aqueous phase. The combined organic phases are washed with water, dried over magnesium sulfate and the solvent is evaported. The 3-benzyloxy-4-methoxyphenyl formate is recrystallized from 95% by weight ethanol.

The 3-benzyloxy-4-methoxyphenyl formate is then converted to 3-benzyloxy-4-methoxyphenol by the following reaction. A mixture of 3-benzyloxy-4-methoxyphenyl formate, methanol and 1M sodium hydroxide in a weight ratio of 1:6:10 is heated under reflux conditions for one hour, the mixture is allowed to cool and an equal volume of water is added. The solution is washed with ether and acidified to pH 3 with concentrated hydrochloric acid. The resulting mixture is extracted with ether. The combined extracts are washed with water and dried over magnesium sulphate and the solvent is evaporated to yield a tan solid which is 3-benzyloxy-4 -methoxyphenol.

The 3-benzyloxy-4-methoxyphenol is reacted with the R₁ chloroformate as follows. The phenol (1.0 equiv.) and triethylamine (1.1 equiv.) are first dissolved in methylene chloride. The R₁ chloroformate (1.1 equiv. ) is added and the mixture is stirred for a number of hours. The solvent is then evaporated and the residue is dissolved in a 1:1 mixture of ether and ethyl acetate. This solution is washed with 1M hydrochloric acid, saturated sodium bicarbonate, and water, and dried over magnesium sulfate. The solvent is evaporated to yield the desired product.

The benzyl protecting group is then removed by catalytic hydrogenation. The above product is dissolved in absolute ethanol and 10 percent palladium on carbon is added. The mixture is placed on a Parr hydrogenator, which is then charged with hydrogen to a pressure of 50 lb./in.². Upon the cessation of hydrogen uptake (approximately 2-5 hours) the mixture is filtered through a celite pad and the solvent evaporated to yield the desired product.

Further details are described in McMurray et al. Journal Chemical Society, pages 1491-8(1960) and Robinson et al. Journal Chemical Society, pages 3163-7 (1931).

The requisite chloroformate of the desired R₁ moiety is either commercially available, known in the art, or prepared from commercially available starting materials by known synthetic procedures.

Commercially available chloroformate precursors can be found in Chem. Sources U.S.A., Directories Publishing Co., Inc. Ormond Beach, Florida as well as Chem. Sources Europe, Chem. Sources Europe Puglisher, Mountain Lakes, New Jersey.

Chloroformates, in general, can be prepared by the reaction of alcohols with phosgene. For a review of this method, as applied to the synthesis of chloroformates, see Matzner, Kurkjy, and Cotter, Chemical Reviews, 64, pages 645-687, (1964).

The phenols used for preparation of the R₁ chloroformates (R₁ OCOCl) are known compounds which are commercially available or are preparable by standard organic preparative methods.

The synthetic procedures disclosed incorporate the benzyl group as a protecting agent for the phenolic hydroxy moiety during various synthetic reactions. Other groups may be employed in place of the benzyl group to achieve this protection. Examples of these groups include 2-methoxyethoxymethyl, methylthiomethyl, t-butyldimethylsilyl, t-butyl ethers, and the 2,2,2-trichloroethyl carbonate. Other protecting groups, as well as specific reaction conditions and references, can be found in "Protective Groups in Organic Synthesis" by Theodora W. Greene, John Wiley & Sons, N.Y., 1981, and in "Protective Groups in Organic Chemistry" by J. F. W. McOmie, Plenum Press, London, 1973.

The present new compounds form salts due to the presence of the phenolic hydroxy group. Thus, metal salts can be formed by reaction with alkali such as aqueous ammonia, alkali and alkaline earth metal compounds such as sodium, potassium, and calcium oxides, hydroxides, carbonates and bicarbonate. The salts are of higher aqueous solubility than the present compound and are useful for purification or isolation of the present products.

The following examples are presented to further illustrate this invention.

EXAMPLE 1 3-Hydroxy-4-methoxyphenyl phenyl carbonate

2.30 Gms. of 3-benzyloxy-4-methoxyphenol and 1.11 gms. of triethylamine was dissolved in 50 ml of methylene chloride and the mixture was stirred at room temperature. To the mixture was added 1.72 gms. of phenyl chloroformate and the resultant mixture was stirred for 2 hours. The reaction was then quenched with 1 ml. of water, and the solvent evaporated. The residue was dissolved in 100 ml. of a 1:1 mixture of ether and ethyl acetate. This solution was washed with equal volumes of 1M hydrochloric acid, saturated sodium bicarbonate, and water, dried over magnesium sulfate, and the solvent evaporated to yield 2.53 gms. of a tan solid which was 3-benzyloxy-4-methoxyphenyl phenyl carbonate.

This compound was deprotected by dissolving 2.45 gms. of the compound in 250 ml. of absolute ethanol and then adding 10% palladium on carbon. This mixture was then placed on a Parr hydrogenator which was then charged with hydrogen gas to a pressure of 50 lb./in². After 3 hours the hydrogen uptake ceased and the mixture was filtered through a Celite pad. The solvent was evaporated to yield 1.42 gms. of a light yellow oil which was 3-hydroxy-4-methoxyphenyl phenyl carbonate. The structure was confirmed using nuclear magnetic resonance (NMR) methods.

A panel of experts determined that a 0.005 weight percent aqueous solution of this product had a sucrose equivalency of 2.5 weight precent.

EXAMPLE 2

A cherry flavored beverage is prepared by mixing 1.48 gms. of an unsweetened cherry flavored instant beverage base mix with 438 gms. of water, 0.13 gms. aspartame (APM) and 0.04 gms. (0.01 weight percent) of 3-hydroxy-4-methoxyphenyl phenyl carbonate. The base contains a malic acid and monocalcium phosphate buffer.

EXAMPLE 3

A vanilla flavored pudding is prepared by mixing 474 gms. of milk, 21.7 gms. of an unsweetened pudding base mix containing 1.35 gms. of sodium acid pyrophosphate, 36.0 gms. sucrose (6.8 weight percent) and 37 mgs. (0.007 weight percent of 3-hydroxy-4-methoxyphenyl phenyl carbonate.

EXAMPLE 4

Additional products are prepared using the procedure of Example 1, but substituting phenyl chloroformate by appropriate chloroformate esters to obtain the following products.

3-hydroxy-4-methoxyphenyl 2-hydroxyphenyl carbonate

3-hydroxy-4-methoxyphenyl 2-methylphenyl carbonate

3-hydroxy-4-methoxyphenyl 3-methylphenyl carbonate

3-hydroxy-4-methoxyphenyl 2-acetylphenyl carbonate

3-hydroxy-4-methoxyphenyl 2,6-dihydroxyphenyl carbonate

3-hydroxy-4-methoxyphenyl 2-methoxyphenyl carbonate

3-hydroxy-4-methoxyphenyl 3-methoxyphenyl carbonate

3-hydroxy-4-methoxyphenyl 2,6-dimethoxyphenyl carbonate

3-hydroxy-4-methoxyphenyl 2,5-dimethylphenyl carbonate

3-hydroxy-4-methoxyphenyl 2,5-dimethoxyphenyl carbonate

3-hydroxy-4-methoxyphenyl 2,6-dimethylphenyl carbonate

3-hydroxy-4-methoxyphenyl 3,5-dimethylphenyl carbonate

3-hydroxy-4-methoxyphenyl 3,5-dimethoxyphenyl carbonate

3-hydroxy-4-methoxyphenyl 2-propylphenyl carbonate

3-hydroxy-4-methoxyphenyl 2-isopropylphenyl carbonate

3-hydroxy-4-methoxyphenyl 2-ethoxyphenyl carbonate

3-hydroxy-4-methoxyphenyl 2-(hydroxymethyl)phenyl carbonate

3-hydroxy-4-methoxyphenyl 2-(hydroxyethyl)phenyl carbonate

3-hydroxy-4-methoxyphenyl 2-methoxymethylphenyl carbonate

3-hydroxy-4-methoxyphenyl 2-methyl-6-methoxyphenyl carbonate

3-hydroxy-4-methoxyphenyl 2-methyl-6-ethylphenyl carbonate

3-hydroxy-4-methoxyphenyl 2,5,6-trimethylphenyl carbonate

3-hydroxy-4-methoxyphenyl 2-methyl-6-hydroxyphenyl carbonate 

What is claimed is:
 1. A compound of the formula: ##STR6## wherein: R is methyl;R₁ is ##STR7## each R₂ is selected from the group consisting of H, OH, CH₃, CH₂ CH₃, OCH₃, Ch₂ OH, CH₂ CH₂ CH₃, CH(OH)CH₃, CH(CH₃)₂, OCH₂ CH₃, CH₂ OCH₃, CH₂ CH₂ OH, COCH₃, COCH₂ CH₃, CH₂ COCH₃, COOH and COOCH₃ ; and each R₃ is selected from the group consisting of H, CH₃, CH₂ CH₃, OCH₃ ; with the proviso that R₁ contain no more than 12 carbon atoms; and salts thereof.
 2. A compound according to claim 1 with the proviso that R₁ contain no more than 10 carbon atoms.
 3. A compound according to claim 1, with the proviso that R₁ contain no more than 8 carbon atoms.
 4. 3-Hydroxy-4-methoxyphenyl phenyl carbonate.
 5. A foodstuff containing a compound of the formula: ##STR8## wherein: R is methyl;R₁ is ##STR9## each R₂ is selected from the group consisting of H, OH, CH₃, CH₂ CH₃, OCH₃, CH₂ OH, CH₂ CH₂ CH₃, CH(OH)CH₃, CH(CH₃)₂, OCH₂ CH₃, CH₂ OCH₃, CH₂ CH₂ OH, COCH₃, COCH₂ CH₃, CH₂ COCH₃, COOH and COOCH₃ ; and each R₃ is selected from the group consisting of H, CH₃, CH₂ CH₃, OCH₃ ; with the proviso that R₁ contain no more than 12 carbon atoms; and salts thereof, said compound being present in an amount effective to perceive sweetness in said foodstuff.
 6. A foodstuff according to claim 5 wherein the foodstuff is a beverage.
 7. A foodstuff according to claim 5 wherein the foodstuff is a gelatin dessert.
 8. A foodstuff according to claim 5 wherein the foodstuff is a milk pudding. 